Carburetor choking device



May 16, 1967 D. F. MORGAN CARBURETOR CHOKING DEVICE 2 Sheets-Sheet l Filed April 19, 1965 ATTORNEY May i6, 1967 l D. F. MORGAN 3,319,943

CARBURETOR CHOKING DEVI CE Filed April 19, 1965 2 Sheets-#Sheet 2 ATTORNEY WITNESS.'

United States Patent Otice 3,319,943 CARBURETOR CHOKING DEVICE Donald F. Morgan, Horseheads, N.Y., assigner to The Bendix Corporation, Elmira, N.Y., a corporation of Delaware Filed Apr. 19, 1965, Ser. No. 449,174 2 Claims. (Cl. 261-39) This invention relates to a carburetor choking device for internal combustion engines. More particularly, this invention relates to an air horn design which cooperates with a choke valve to improve the fuel-air ratio economy during cold engine operation.

An object of the present invention is to increase cold engine fuel economy over the full range of engine speeds, long a source of concern, especially to the automotive industry.

An object of the present invention is to properly enrich the fuel-air mixture of an internal combustion engine over the necessary low speed range when the engine is cold.

An object of the present invention is to properly lean the choke enriched fuel-air mixture of an internal combustion engine over the medium and high speed ranges when the engine is cold.

Another object of the present invention is a fuel-air enrichment device which is operative only during cold engine operation.

A further object is the creation of a compact, efiicient and effective fuel enrichment device which cooperates with choke valves of prior art carburetors.

Prior art carburetor choke mechanisms for internal combustion engines, in providing a sufiiciently rich fuelair mixture for cold engine fast idle speed operation, invariably provide too rich a fuel mixture for cold engine operating conditions above fast idle speed.

The present invention is a highly satisfactory solution to that problem without adding significantly to the cost of carburetor construction.

Other objects and advantages of the present invention will appear from the following description of its construction and operation.

FIGURE l shows a side view, partly broken away, of an embodiment of the present invention.

FIGURE 2 shows a top view of an embodiment of the present invention with the choke valve and mounting rod removed.

FIGURE 3 shows a side view of an embodiment of the present invention showing the manifold vacuum responsive device and the temperature responsive device and the mechanical inter-relationship between the two.

FIGURE 4 shows a graph comparing the performance of an embodiment of the present invention used in an automotive carburetor to a prior art automotive carburetor.

Referring now to FIGURE l, the numeral indicates generally a carburetor for an internal combustion engine having an air horn 12, an induction passage 14, and a choke valve 16 of the offset type pivoted by a shaft 18 journalled through the air horn 12. A main body 20 is attached to the air horn 12. The main body 20 has a mixture passage 22 which communicates with the induction passage 14. A fuel chamber (not shown) into which fuel is received through a fuel inlet orifice 26 in the conventional manner is contained in the main body 20. The float chamber is vented to atmospheric pressure by a vent (not shown).

A primary venturi 28 is formed in the mixture passage 22. A primary fuel discharge jet assembly 29, communicating with the fuel chamber, supplies fuel to the mixture passage 22. A secondary venturi 30 is disposed in the mixture passage 22.

A throttle body 31 is attached to the main body 20.

3,319,943 Patented May 16, 1967 The throttle body 31 has a fuel-air passage 32 communicating with the mixture passage 22 and a throttle valev 34 pivoted by a shaft 36 in the fuel-air passage 32. The throttle valve 34 controls engine speed.

The offset choke valve 16 has a major portion 17 and a minor portion 19. The major portion 17 extends downstream in the induction passage 14 and the minor portion 19 extends upstream in the induction passage 14 when the choke Valve 16 is rotated from its closed position as indicated when the choke valve is in the position shown.

A shelf 38 is formed in the induction passage downstream of the choke valve 16 at a distance from the shaft 1S slightly greater than the radius of the major portion 17 of the choke valve. When the major portion 17 of the choke valve is partially rotated downstream and the minor portion rotated upstream (i.e., when the choke valve 16 is in the position shown by the dotted line 21), two flow paths are formed as shown `by the larrows 40 and 42. The first ow path, shown by the arrow 46, is defined by the major portion 17 of the choke valve, the adjacent portion of the induction passage 14 and the shelf 38. The second flow path, shown by the arrow 42, is formed by the minor portion 19 of the choke valve and the adjacent portion of the induction passage 14. The first ow path 4t) is a more restricted flow path than the second flow path 42. The separation between the shelf 38- and the major portion 17 of the choke valve, while relatively small, can be adjusted to suit the desired function of any carburetor.

The shelf 38, las shown in FIGURE 2, extends around a portion of the periphery of the induction passage 14. The peripheral extent of the shelf is determined by the extent of restriction desired in ow path 4t). The extent of shelf projection across the induction passage 22 is variable in accordance with the desired operating performance of the choke. As seen in FIGURE l, the shelf 38 in this embodiment extends downstream in the induction passage 14 to the bottom edge of the air horn. The downstream extent of the shelf may be varied to suit design factors with respect to location of the secondary venturi and the primary fuel discharge jet assembly and with respect to air flow pattern desired within the air horn and mixture passage.

A pneumatic intake manifold pressure responsive device 46 and a thermostatic engine temperature responsive device 56 (shown in FIGURE 3) are attached to the choke valve 16 through the pivot shaft 18. The intake manifold vacuum responsive device consists of an inlet tube 48 vented to the intake manifold (not shown), an outer shell 49 with `a bias `spring Si) and a flexible diaphragm S1. The flexible diaphragm 51 outer surface is vented at 52 to atmospheric pressure. The flexible diaphragm 51 is connected to a first rod 53 leading through the outer case 49 which is connected to a second rod 54.

The thermostatic engine temperature responsive device 56 consists of an outer case 57 attached to the exhaust manifold (not shown). A bimetallic spring 58 is fixed at one end to the case 57 and at the other end to a rod 59. A mounting lever 60 is connected to the choke mounting rod 18. The thermostatically-controlled rod 59 is fastened to the lever 60. An arcuate slot 62 is cut in the lever 60 to receive the second rod 54 controlled by the intake manifold vacuum responsive device 46.

When the engine cools down, the bimetallic spring 58 closes the choke valve 16, reducing the air flow through the induction passage 14. When the engine is then started, the intake manifold vacuum-controlled device 46 partially opens the choke valve 16. A fast idle cam (not shown), similar to one disclosed in U.S. Patent 2,867,424 issued to Sutton, controls the engine fast idle speed by holding the throttle valve 34 slightly open. At fast idle speed, the intake manifold vacuum responsive device 46 is operative to 3 hold the choke valve 16 open in the position shown by the dotted line 21 in FIGURE l, a position known as the vacuum kick position.

There are various other types of choke valve controls Well known in the art which control choke valve orientation within the induction passage in response to engine temperature and engine intake vacuum. The particular controls illustrated and described are shown only as examples of a type of control which may be used in conjunction with a shelf-type air horn.

In the operation of internal combustion engines below normal operating temperatures, it is necessary to have an enriched fuel-air mixture. It is desirable that this enriched fuel-air mixture ratio remain fairly constant over the low to low medium engine speed range. As the engine speed range increases from low-medium to high speed, it is desirable that the fuel-air mixture ratio become more lean approaching normal running mixtures.

In general, the fuel-air mixture ratio is controlled by the volume, velyogityppressure-and flow path of the air through theinduction passage and mixture passage.

In the shelf-type carburetor, the vacuum kick position of the choke valve 16 is a more wide open position than is the vacuum kick position of prior art carburetors. In this position, the first fiow path 40 is a more restricted flow path than the second flow path 42. Thus, more air is drawn past the minor portion 19 of the choke valve than is drawn past the major portion 17 of the choke valve. The shelf-type carburetor is capable of better air flow direction control to the primary fuel discharge jets 29 and to the primary 2S and secondary 30 venturis than prior art carburetors. Further, the first restricted flow path 40 creates another source of partial vacuum which affects the fuel-air ratio. An offset choke valve will tend to open as air ow increases. The partial vacuum created by the first restricted flow path 40 vacuum affects not only the fuel feed through the fuel `discharge jet 29, but tends to open the offset choke valve more rapidly than is customary in a prior art choke valve due to the effects of air flow past the choke valve 16.

The net result of the more open vacuum kick position of the choke valve, the increased rapidity of opening of the offset choke valve, the better directed and controlled air-flow and the finer control over air volume, pressure and velocity is that a carburetor using the shelftype air horn gives a far more desirable fuel-air ratio operating characteristic for cold engine operation. This result is shown in FIGURE 4 where curve 70 is that of a carburetor using a standard air horn Without a shelf and curve 72 is that of a carburetor using a shelf-type air horn in cold engine operation of an automobile engine. The mixture ratio in pounds of fuel per pounds of air is plotted on the vertical axis and the air ow in pounds per hours is plotted on the horizontal axis. Air flow of 75 pounds per hour corresponds to the fast idle speed set by a fast idle cam. Both carburetors start at the desired fuel-air richness ratio of l2. The carburetor using the non-shelf type air horn (curve 76) rapidly enriches the fuel-air mixture ratio as engine speed increases to the low-medium speed range of 150 pounds per hour. At this point, the offset choke valve opens slightly due to air pressure acting on the unbalanced choke valve, causing the richness of the fuelair ratio to drop. The shelf-type air horn, carburetor (curve 72) is adjusted to start at the same idle point of 75 pounds of air per hour and a fuel-air ratio of l2. The fuel-air ratio increases much less rapidly until an air-flow ratio of about 125 pounds per hour is reached. At this point, the offset choke valve is beginning to be opened more widely by the air flow caused by the shelf and the increase in fuel-air ratio levels off. At an air-flow rate of about 150 pounds per hour, the fuel-air ratio decreases as the air pressure on the offset choke valve causes the choke valve to open still more. Y

It can be seen from the description of operation and the graph shown in FIGURE 4, that a carburetor employing a shelf-type air horn provides a fuel-air ratio of the necessary richness at fast idle speed for a cold engine and a more economical fuel-air ratio at any increased engine speed up through the high engine speed range. As the engine warms up, the thermostatic control opens the choke valve more widely, reducing the effect of the shelf. Warm engine operation of a shelf-type air horn in a carburetor is the same as warm engine operation of prior art air horns.

It can be readily seen that what has been described is an eicient, effective and inexpensive device for providing a more nearly ideal fuel-air mixture for cold internal combustion engines. The devices described can be readily used with prior art chokes and choke temperature and pressure controls. The device is operative only during cold engine operation. The device promotes greater cold engine fuel economy by matching the choke-enriched mixtures more-closely-to'th'e Vactual engine requirements than prior art devices.

The present invention is not limited to the details of construction and operation described in this specification and the drawings. It is to be understood that various other arrangements of parts may be made without departing from the spirit and scope of the invention.

I claim:

1. A carburetor for an internal combustion engine comprising:

an air horn having an induction passage therethrough;

shaft means extending through said induction passage;

a choke plate pivotally mounted on said shaft means in said induction passage capable of controlling air flow therethrough;

temperature responsive means connected to said choke plate operative when cold to bias said `choke plate in a closed direction;

manifold vacuum responsive means connected to said choke plate operative to partially open said choke plate in opposition to said temperature responsive means to establish a choke plate vacuum kick position for cold idle engine conditions;

said choke plate eccentrically mounted on said shaft means to provide a major portion a-nd a minor portion of said choke plate;

a first flow path defined by said major portion and said induction passage;

a second fiow path defined lby said minor portion and said induction passage;

a shelf means downstream of said major portion cooperative with said major portion to restrict the air fiow through said first fiow path through a range of choke plate positions from closed through vacuum kick positions.

2. A carburetor for -an internal combustion engine comprising:

lan air horn having an induction passage therethrough;

a shaft journalled in `said induction passage;

a choke plate mounted for rotation on said shaft within said induction passage, said choke plate eccentrically mounted within said passage having a major portion and a minor portion;

a shelf means disposed downstream in said passage at a distance slightly greater than the radius of said major portion from said shaft;

a first variable flow path defined by said major portion,

said induction passage and said shelf means;

a second variable flow path defined by said minor portion and said induction passage;

a main body having a mixture passage therethrough communicating with said rst and second flow paths;

primary venturi means disposed in said mixture passage;

secondary venturi means disposed in said mixture passage;

fuel supply means disposed in said mixture passage;

thermostatic means for controlling the orientation of said choke plate in said induction passage in a closed direction responsive to engine temperature;

manifold vacuum means for controlling the orientation of said choke plate in said induction passage to establish a partially open position for engine cold idle operation, said manifold vacuum means capable of partially overcoming said thermostatic means; and

said shelf means cooperative with said major portion of said choke plate throughout a range of positions from closed through the partially opened cold idle position to restrict `air ow through said first variable flow path.

References Cited by the Examiner UNITED STATES PATENTS Linga 261-39 Hunt et a1. 261-39 Winkler 261-39 Meyer 261- 65 X Carlson 261-39 Sarto 261-39 Landrum 261-65 Wise 261-39 HARRY B. THORNTON, Primary Examiner. T. R. MILES, Assistant Examiner. 

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE COMPRISING: AN AIR HORN HAVING AN INDUCTION PASSAGE THERETHROUGH; SHAFT MEANS EXTENDING THROUGH SAID INDUCTION PASSAGE; A CHOKE PLATE PIVOTALLY MOUNTED ON SAID SHAFT MEANS IN SAID INDUCTION PASSAGE CAPABLE OF CONTROLLING AIR FLOW THERETHROUGH; TEMPERATURE RESPONSIVE MEANS CONNECTED TO SAID CHOKE PLATE OPERATIVE WHEN COLD TO BIAS SAID CHOKE PLATE IN A CLOSED DIRECTION; MANIFOLD VACUUM RESPONSIVE MEANS CONNECTED TO SAID CHOKE PLATE OPERATIVE TO PARTIALLY OPEN SAID CHOKE PLATE IN OPPOSITION TO SAID TEMPERATURE RESPONSIVE MEANS TO ESTABLISH A CHOKE PLATE VACUUM KICK POSITION FOR COLD IDLE ENGINE CONDITIONS; SAID CHOKE PLATE ECCENTRICALLY MOUNTED ON SAID SHAFT MEANS TO PROVIDE A MAJOR PORTION AND A MINOR PORTION OF SAID CHOKE PLATE; A FIRST FLOW PATH DEFINED BY SAID MAJOR PORTION AND SAID INDUCTION PASSAGE; A SECOND FLOW PATH DEFINED BY SAID MINOR PORTION AND SAID INDUCTION PASSAGE; A SHELF MEANS DOWNSTREAM OF SAID MAJOR PORTION COOPERATIVE WITH SAID MAJOR PORTION TO RESTRICT THE AIR FLOW THROUGH SAID FIRST FLOW PATH THROUGH A RANGE OF CHOKE PLATE POSITIONS FROM CLOSED THROUGH VACUUM KICK POSITIONS. 